The present invention relates to the medical field of wound care or wound healing, in particular based on local application of a wound dressing.
In particular, the present invention relates to a wound dressing which is preferably suitable for therapeutic wound care of the human or animal body.
The present invention further relates to use of the wound dressing according to the invention for therapeutic wound care.
According to medical definition and in the context of the present invention, a wound is understood to mean a break in the continuity of body tissues with or without substance loss, such a break in general being caused by mechanical injuries or physically caused cell damage.
Wounds are classified into various types depending on their causes. Thus wounds created by external trauma are classed as mechanical wounds, these mainly being cutting and piercing wounds, crushing, laceration, scratch and abrasion wounds. Another form of wounds is described as thermal wounds, which are caused by the action of extreme heat or cold. In contrast, chemical wounds are caused by the action of chemicals, in particular by erosion by acids or alkalis. Tissue breaks or damage which arise under the action of actinic radiation, e.g. ultraviolet radiation and/or ionizing radiation, are described as radiation wounds.
In addition, depending on the physiological condition, a distinction is also made between necrotizing, infected and/or chronic or acute wounds.
For further details on the term “wound”, reference can be made to Pschyrembel—Clinical Dictionary, 257th edition, 1994, Verlag de Gruyter, Berlin/New York, page 1679, keyword “wound”, the entire content whereof relating to this is by reference completely included herein.
Wound healing, i.e. the physiological processes for the regeneration of the destroyed tissue and for closure of the wound, takes place in particular by regeneration of connective tissue and capillaries for the circulation, during which in general three phases are passed through. This process can extend over a period of up to four weeks depending on the size and depth of the wound.
In the first phase, also described as latency or inflammatory phase, within the first hours after wounding has occurred, firstly exudation of body fluids takes place, in particular of blood, to free the wound opening from foreign bodies, germs and dead tissue. Next, a scab, which protects the wound externally from the penetration of germs and foreign bodies is formed through clotting of the blood that has emerged. After the formation of the scab, the resorption phase of the latency phase begins, in which a catabolic autolysis also takes place, i.e. macrophages migrate into the wound tissue and phagocytize the coagulated blood in the wound opening. Foreign bodies or microorganisms which may have penetrated are degraded in this phase, which can be associated with mild to moderate inflammatory symptoms. Further, in the resorption phase the build-up of the basal epithelium and of granulation tissue begins. After about one to three days after causation of the wound, the latency phase is generally completed and the latency phase passes into the second phase, the so-called proliferation or granulation phase, which in general lasts from the fourth to the seventh day after the injury. During this, the anabolic repair, which in particular refers to the formation of collagen by fibroblasts, begins. In the repair or epithelization phase, which begins from about the eighth day after the occurrence of the wound, final scar tissue is formed and the squamous epithelium of the skin is renewed. The scar tissue formed has neither sebaceous nor sweat glands and appears white to mother-of-pearl on the skin. In contrast to undamaged tissue, the collagen in the scar tissue is no longer complexly linked, but instead aligned parallel.
For further information on the term “wound healing”, reference can be made to Pschyrembel—Clinical Dictionary, 257th edition, 1994, Verlag de Gruyter, Berlin/New York, page 1670, keyword “wound healing”, the entire content whereof relating to this is by reference completely included herein.
In the prior art, many medical articles and objects and therapeutic measures are known which serve to support or accelerate wound healing. Nevertheless, complications or impeded healing often occur, in particular when the wound is very extensive or many tissue layers are affected.
A relatively commonly occurring complication in wound healing are wound infections triggered by bacteria, fungi or viruses, which are attributable in particular to defective wound hygiene or increased occurrence of germs, such as is often the case in hospitals. Through contamination with various microorganisms, in particular bacterial infections of the wound can occur, during which because of the infection classical signs of local inflammation arise, such as pain, swelling, reddening and overheating. In the worst case, however, as a result of phlegmonous, i.e. extensive, dissemination, a general infection or life-threatening sepsis can occur with high fever and chills. In the causation of wound infections, the so-called hospital germs, such as Proteus mirabilis, Pseudomonas aeruginosa, Staphylococcus epidermidis, Staphylococcus aureus and Escherichia coli play a significant part. A particular problem with such infections with hospital germs are the many antibiotic resistances acquired by the strains concerned in the course of time, as a result of which infections arising can only be treated with extreme difficulty, above all in patients with an already weakened immune system. Numerous strains exist of Staphylococcus aureus in particular which have resistance to all beta-lactam antibiotics obtainable on the market, such as methicillin and oxacillin, and various other antibiotic classes such as glycopeptide antibiotics, sulfonamides, quinolones or tetracyclines. Consequently, in case of infections with such germs a therapy independent of the administration of antibiotics must be given to avoid systemic dissemination of the pathogen in the body. However there is still a serious lack of such therapeutic concepts in the state of the art, so that the death rate due to multiresistant hospital germs exceeds the mortality rate due to seasonal influenza.
A further problem in wound healing can be the formation of necroses, during which the pathological death of cells on the living body takes place. In the case of necroses, successful therapy mostly necessitates a debridement, which means the excision of the dead tissue and serves for stimulation of wound healing and avoidance of dissemination of a wound infection. A debridement can be effected both surgically, e.g. with scalpel and ring curette, and also enzymatically, autolytically or biosurgically. However, such treatment is mostly associated with severe pain for the patients, especially in the case of surgical debridement.
Particularly intensive and careful therapeutic measures are necessary when an acute wound turns into a chronic wound. A wound is considered chronic when its healing is not completed within a period of four to eight weeks after occurrence. Chronic wounds mostly do not occur by chance, but instead often arise in connection with clinical pictures which are associated with a weakened immune system or defective circulation. The diseases associated with poor circulation mainly of the legs include in particular type 2 diabetes mellitus, chronic venous insufficiency or peripheral occlusive arterial disease, which is also known as the so-called “claudication”. In case of the aforesaid diseases, an extensive, poorly healing and infected or necrotizing chronic wound can develop even from very small wounds. In particular with infection of such wounds with microorganisms, for example the aforesaid hospital germs, complete necrosis of skin, subcutis and muscle fascia can occur, which in the worst case renders amputation of the limbs affected necessary. Particularly commonly in connection with circulatory disorders, the diabetic foot syndrome occurs, a necrotizing fasciitis or Ulcus cruris. Immunodeficiency, for example in HIV infected patients, can favor the occurrence of chronic wounds, since firstly the infection risk as such is elevated and secondly the regeneration of tissue for closure of the wounds only takes place slowly. The pressure ulcers also described as bedsores, such as mostly occur in bedridden patients because of incorrect positioning, are also termed chronic wounds, since the time for their healing also extends beyond a period of four weeks and requires particularly careful and prolonged therapeutic measures.
Wound care or wound treatment generally pursues the aim of preventing a wound infection and ensuring rapid and effective wound healing. Here how intensively and by what measures the wound healing must be supported depends on the severity, in particular the depth and area, of the wound.
Already in 1979, the American doctor T D Turner drafted various, generally recognized quality criteria for the ideal wound dressing, which even today still retain their validity.
However, the approaches for wound care or for accelerating wound healing known from the state of the art are often inadequate, since they are in many cases not satisfactory as regards the generally recognized quality criteria for wound dressings or do not enable adequate therapeutic success.
In EP 2 322 232 A 2, a multilayer wound dressing is described which is based on a polysaccharide-containing gel and an additional layer based on another biocompatible material. However, such gel-based wound dressings are also associated with the disadvantage that owing to the already high moisture content of the gel itself, only diminished uptake of excess secretions can occur. In particular, however, wound dressings of this type also above all fail to provide a bacteriostatic/bactericidal effect sufficient to ensure efficient contamination control with regard to microorganisms.
DE 10 2007 030 931 A1 further describes a wound dressing comprising inter alia a disinfecting/decontaminating or protease-inhibiting substance. However, a wound dressing of this type cannot be used to achieve adequate odor adsorption. Above all, however, the but low bacteriostatic effect means that the protection from contaminants is insufficient for efficient prevention of infections.
DE 10 2006 050 806 A1 further describes wound dressings comprising a carbonaceous material impregnated with noble metals, in particular silver, to improve the bacteriostatic effect. This does achieve better protection from contaminants compared with the wound dressings described above. However, the noble metals used present a significantly heightened risk of adverse effects, since many noble metals, including silver in particular, are cell penetrating and suspected of playing a part in Alzheimer's and Parkinson's, since they are capable of damaging the insulator proteins surrounding nerves. In addition, the admittedly antimicrobial effect of the noble metal-impregnated carbonaceous material offers nothing by way of sustained hastening of wound healing.
In addition, DE 38 75 217 T2 corresponding to EP 0 311 364 B1 relates to a wound dressing which includes an activated carbon layer wherein at least 10% of the total pore volume of the activated carbon should be formed of mesopores, and said wound dressing should be contained sterile and in a bacteria-proof covering. The activated carbon is further advantageously impregnated with an antimicrobial agent, such as silver. The disadvantages of silver-impregnated activated carbon were discussed above. In addition, a predominantly mesoporous activated carbon is incapable of immobilizing microorganisms durably, so the bacteriostatic effect is not always sufficient. Nor does this wound dressing have any wound healing promoter effect.
There is accordingly a need for wound care dressings which possess improved contamination control, improved odor adsorption to remove unpleasant odors and also a superior absorption of excess exudates, in particular wound fluid.